docs: def __set_formulas(self, formulas):
          """
          Sets formulas in this cell range from an iterable of iterables.
  
          Any cell values can be set using this method. Actual formulas must
          start with an equal sign.
          """
          # Tuple of tuples is required
          array = tuple(tuple(self._clean_formula(col) for col in row) for row in formulas)
          self._get_target().setFormulaArray(array)